Git & GitHub

Why does Git exist?

Imagine writing a long document with three teammates. Everyone edits the same file. One person accidentally deletes a section. Another person's version overwrites your work. By the end of the week, your folder looks like this:

report_v2_final_FINAL_cedric.docx
report_v2_final_FINAL_cedric_REVISED.docx
report_v2_final_FINAL_cedric_REVISED_2.docx

And nobody is sure which one is correct.

Now imagine the opposite: every change is tracked. You can see exactly who changed what, and when. If something breaks, you can go back to any earlier version in seconds. When two people edit different parts at the same time, the changes merge automatically. And if you want to try a risky new idea, you do it on a separate "copy" so the working version is never touched.

That is what Git does — except for code instead of documents.

GitHub is where your Git history lives online: backed up, shareable, and visible to anyone you want to impress or collaborate with.

For data analysts, this is not optional. Your SQL models, your dbt project, your analysis scripts — all of it belongs in Git. It is how teams share code without stepping on each other, and how you show your work to future employers.

Prerequisite

Complete the Terminal course first. You should be comfortable with cd, ls, mkdir, cat, and basic file editing before starting here.

How this works: you build a real repo

The SQL and Terminal courses give you an in-browser playground. Git is deliberately different — the whole point of Git is doing it for real, against your own GitHub account, so a simulator would defeat the purpose.

Instead, you build one real project as you go. At key milestones you hit a 🚩 Checkpoint page: a short, copy-along exercise that adds to a repo called my-data-portfolio and pushes it to your own GitHub. You will make real commits, hit real errors, and fix them — exactly like you will on the job.

By the end, your repo looks like this, and every file is there because you created and pushed it:

my-data-portfolio/
├── README.md
├── queries/
│   └── monthly_sales.sql
├── notes/
│   └── findings.md
└── .gitignore

The five checkpoints, spread across the course:

Checkpoint	You will
🚩 Make Your Repo	Create the repo locally and make your first commits
🚩 Push It Live	Put it on GitHub and see your README online
🚩 Branch + PR	Add a SQL file through a real pull request
🚩 Break & Recover	Cause a conflict on purpose, then recover from it
🚩 Polish Your Repo	Turn it into a portfolio piece with a tagged release

It is meant to be hands-on

When you finish, this is a real repo on your GitHub profile that you can show people. Run every command — do not just read along.

What You'll Learn

• Install and configure Git on your machine
• Create repos, stage changes, and write commits
• Publish your work to GitHub and keep it in sync
• Work in branches and open pull requests
• Resolve merge conflicts safely
• Undo mistakes without losing work
• Rebase for a clean commit history
• Use GitHub features: Issues, Actions, Releases

Lessons

Lesson	What you do
Setup	Install Git, configure identity, create GitHub account, set up SSH
Initialize a Repo	git init, git status, your first file
Stage and Commit	git add, git commit, git log
Connecting to GitHub	Create a remote, push your first commit
Inspect Changes	git diff, selective staging, readable log
Amend and Practice	Fix the last commit, run the full loop
Branching	Create branches, switch between them, push a branch
Pull Requests	Open, review, merge, and clean up a PR
Working Across Machines	Clone, pull, fetch, and fork
Merge Conflicts	Create, read, and resolve a conflict
Undo Mistakes	Stash, restore, reset, revert, reflog
Rebasing	Rebase, interactive rebase, the golden rule
GitHub Workflows	README, .gitignore, tags, issues, Actions
Portfolio Polish	Profile README, pinned repos, open-source contribution

How to read these lessons

Each lesson lists the commands to run. Run every one. If you skip ahead without practicing, you will forget the muscle memory. Git rewards repetition.